Virginia plays along, and I give several experimental pushes. Sometimes as I push, I think, You're a terrible person! Sometimes I think, You're fabulous! I try to keep the pressure consistent and my face expressionless. Just as I expect, Virginia's arm feels much stronger when I'm thinking positive thoughts about her. When my thoughts are negative, she's as weak as a kitten.

Virginia doesn't like this. She frowns and demands many repeats, just as I did when I learned this homespun experiment from two social-scientist friends. I was stunned at how noodle-like my arm became when my friends thought negative things about me. Since then I've repeated this process with dozens of clients. When speaking to groups, I often choose two volunteers (one pusher, one pushee), who test their strength as everyone else in the room thinks critical or supportive thoughts about the person being pushed. I give the crowd random hand signals—thumbs up for nice vibes, thumbs down for mean ones—that can't be seen by the volunteers. The group's thoughts should not affect the subject's strength. But they almost always do.

Grab some friends and try this experiment yourself. If your group is anything like the ones I've worked with, you or your compadres will find your arm strength varying in response to one another's thoughts. Perhaps one of you will insist that this shift happens because you were communicating subtle cues through facial expression, body language, or some other physical action. Could be true, but whatever the mechanism—telephone telepathy or imperceptible physical signs—the fact is that many people are sitting ducks for social contagion.

If this experiment doesn't affect you—if your arm strength doesn't vary depending on what other people are thinking—feel free to become a repossession officer or divorce lawyer. What the heck, run for president. You'll continually interact with people who dislike you, but it won't bother you a bit.

Shielding yourself from a coworker's or family member's stress or high-pitch negativity requires constructing a suit of psychological armor. Most of my clients, Virginia included, can do this simply by visualizing a situation in which they feel deeply calm. Picturing the best day you spent with your funniest friend or remembering a day at the beach with your dog might be enough protection for you.

Extremely spongy people may have to try a number of visualizations before finding the right defense. Check for effectiveness with the arm test: Ask your friends to come back over; keep holding different positive images in your mind's eye until you find that your arm is able to retain its muscle strength no matter what ugly thoughts others are sending your way. The delightful thing about this kind of safeguard is that it allows nourishing energy to reach you but deflects the stuff that's poisonous.